Python Decorator Clock Implementation

#decorator #designpattern #apply #python #programming

def clock(func):
    def clocked(*args):
        t0 = time.perf_counter()
        result = func(*args)
        elapsed = time.perf_counter() - t0
        name = func.__name__
        arg_str = ', '.join(repr(arg) for arg in args)
        print(f'[{elapsed:0.8f}s] {name}({arg_str}) -> {result!r}')
        return result
    return clocked

@clock
def factorial(n)
	return if n < 2 else n * factorial(n-1)

The function above becomes: factorial = clock(factorial)
- In other words, the factorial becomes a reference to clocked function

>>> import clockdeco_demo
>>> clockdeco_demo.factorial.__name__.'clocked'

The function accept the same arguments but return what the decorator want to return. Make some extra processing with the decorator.
To support keyword arguments you have to use functools.wraps(func)

def clock(func):
    @functools.wraps(func)
    def clocked(*args, **kwargs):
        t0 = time.perf_counter()
        result = func(*args, **kwargs)
        elapsed = time.perf_counter() - t0
        name = func.__name__
        arg_lst = [repr(arg) for arg in args]
        arg_lst.extend(f'{k}={v!r}' for k, v in kwargs.items())
        arg_str = ', '.join(arg_lst)
        print(f'[{elapsed:0.8f}s] {name}({arg_str}) -> {result!r}')
        return result
    return clocked

There is a version with parameters: Python Decorator Clock Implementation with Parameters

References

Ramalho, 2022, p317-319